a) Field of the Invention
This invention relates to a charge mosaic membrane permitting permeation of an electrolyte therethrough, a process for the production of the charge mosaic membrane, a method of use of the charge mosaic membrane, and an apparatus provided with the charge mosaic membrane.
b) Description of the Related Art
Charge mosaic membranes through each of which cationic polymer domains and anionic polymer domains extend in a substantially alternating arrangement relative to the direction of the thickness of the membrane are known to date. These known membranes have a function that they can dialyze electrolytes of low molecular weights but they cannot dialyze nonelectrolytes or have very low dialysis rates for such nonelectrolytes.
As a process for the production of such a charge mosaic membrane, it has been proposed to use a block copolymer or to use at least one of a cationic polymer and an anionic polymer in the form of fine polymer particles. The production process making use of the block copolymer is very difficult to practice. In contrast, the production process in which at least one of the cationic polymer and the anionic polymer is used in the form of fine polymer particles has a merit in that the production is very easy.
In the above-described process making use of fine polymer particles, use of the fine polymer particles in the form of microspheres makes it possible to rather easily produce a charge mosaic membrane owing to the inherent close packability and isotropy of the microspheres. Nonetheless, this process is accompanied by a problem for the production of a membrane of large area, because most components of the membrane are ionic polymers and the membrane so formed tends to shrink or lose strength upon drying.
As a process which reduces the above problem, a process making use of a pliable polymer component as a matrix component for a charge mosaic membrane is proposed in JP kokai No. 10-87855. This process has facilitated the production of a charge mosaic membrane of large area while providing the charge mosaic membrane with improved durability and handling during use. However, this process requires long time for the formation of the membrane, is not fully satisfactory in the stability of a mixture or dispersion of a cationic polymer component and an anionic polymer component (both of the polymer components may hereinafter be called xe2x80x9ccharged polymer componentsxe2x80x9d), and furthermore, has difficulty in producing a thin membrane having a uniform thickness.
An object of the present invention is therefore to provide a charge mosaic membrane making use of charged polymer particles, which can be produced with ease and has excellent selective permeability, and also a process for the production of a charge mosaic membrane having a uniform and small thickness, which requires short time for the formation of the membrane and is excellent in the stability of a mixture or dispersion of the charged polymer components and a matrix component.
To achieve the above-described object, the present invention therefore provides: in an aspect thereof, a charge mosaic membrane comprising a cationic polymer component, an anionic polymer component and a matrix component, wherein both of the cationic polymer component and the anionic polymer component are crosslinked particulate polymers; and the matrix component is at least one polymer selected from a polysulfone resin, a polyarylate resin, a polyamide resin, a polyimide resin, a polyamideimide resin, a polyurethane resin, a fluorinated resin or a silicone resin; in any other aspect thereof, a process for the production of the charge mosaic membrane, which comprises conducting formation of the membrane by using a composition in which the cationic polymer component and the anionic polymer component are both dispersed in a solution of the matrix component in an organic solvent; in a further aspect thereof, a method of use of the charge mosaic membrane, which comprises using the membrane for permeation of an electrolyte; and in a still further aspect thereof, an apparatus provided with the charge mosaic membrane.
The charge mosaic membrane according to the present invention is excellent in physical properties such as chemical resistance, solvent resistance and waterproofness, is chemically stable, has durability against hydrolysis and oxidative degradation, and possesses superb selective permeability.
According to the production process of the present invention, the domain-forming, charged polymer components are both used in the form of the crosslinked particulate polymers, and at least one polymer selected from the polysulfone resin, the polyarylate resin, the polyamide resin, the polyimide resin, the polyamideimide resin, the polyurethane resin, the fluorinated resin or the silicone resin is used as the matrix forming polymer component. Upon formation of the membrane, the crosslinked particulate polymers as the charged polymer components are used in the form of the composition in which the crosslinked particulate polymers are dispersed in the solution of the matrix component in the organic solvent. This production process can therefore form a thin charge mosaic membrane having a uniform thickness in a short membrane-forming time while enjoying excellent stability of the mixture, i.e., dispersion of the charged polymer components and the matrix component.
Therefore, the charge mosaic membrane according to the present invention can be used for the selective permeation of an electrolyte, for example, for the transport, separation, concentration, absorption or the like of an electrolyte.